ROOT DISEASES 147 



F. W. South was evidently due, in part at least, to this fungus. 

 In addition to its wide range on herbaceous hosts the fungus has 

 occurred in the West Indies on seedling citrus plants, both in the 

 seed-bed and the nursery. In the United States it has been re- 

 corded from sweet potato. On sugar-cane it gives rise to a disease 

 of a special type, red-rot of the leaf-sheath, described with the 

 diseases of that crop. 

 Control. 



The only apparent hope of dealing with the disease is through 

 measures designed to prevent its appearance by reducing humidity, 

 which include close surface draining, wide spacing, and the 

 provision of support for climbing plants. Access of sun and air 

 are very effective checks to the fungus. Affected plants should 

 be promptly pulled up, and in this case should certainly be 

 burnt. The application of lime to the soil has been recommended. 



FoMES Root Rot. 



The large bracket fungus Fomes (Polyporus) hicidus (Leys) 

 Fr. has come to notice from time to time as a suspected parasite 

 working on the roots and collar of various trees. 



F. W. South regarded it as taking part in the destruction of 

 lime trees in Montserrat and Antigua, but it is impossible to say 

 what is its real position amongst the other factors contributing to 

 the death of the trees. (See Diplodia Dieback.) 



A case in which, owing to the absence of compHcations, the 

 connection of this fungus with root disease was more clearly 

 indicated received some attention from the writer in St. Kitts in 

 1914. At the Basseterre Botanic Gardens a row of large 

 Saman trees {Pithecolobium Saman) was thinned out by cutting 

 down alternate trees. About a year afterwards three of the 

 remaining trees died with a fungus rot of the roots, and an 

 adjacent hedge of bread-and-cheese (P. imguis-cati) was similarly 

 killed. The Saman trees have continued to die one by one. 

 White mycelium is plentifully developed, in some places in thick 

 masses, under the bark of the collar and roots, and large sporo- 

 phores of Fomes hicidus regularly grow out from this when 

 the tree is dying or dead. The bracket-like fructifications attain 

 in well-grown examples to a diameter of 30 centimetres. They 

 are usually supported on short thick reddish-black polished 

 stalks, single or fused ; the upper surface is irregularly wrinkled and 

 has the appearance of being coated with brownish-red lacquer ; 

 while the underside when fresh is whitish or buff in colour. 



The fungus has a similar status in other countries. T. Fetch 

 has found it in association with root diseases of coconut, mango, 

 and flamboyante in Ceylon ; P. J. van Breemen suspects it to 

 be the cause of a white rot of Ccesalpinia coriaria and Acacia 

 tortuosa in Curagoa, and P. A. van der Bijl attributes to it the 

 death of Acacia spp. in South Africa. It will be seen that there 

 is some cumulative evidence of its parasitism on leguminous trees. 



